The core of a vehicle's internal combustion engine is its cylinders. Combustion of gases and other combustion materials occurs within the cylinders and effectuates the movement of pistons whose power is transferred to the vehicle's driveshaft. The cylinders each include multiple valves that allow the various combustion products and exhaust into and out of the combustion chamber. The proper operation of these valves is crucial to provide the appropriate mix of combustion products at the appropriate times in the combustion chambers in order to produce optimal power from the engine.
Historically, the cylinders were completely encased in an engine block. The engine block was a machined casting that included not only the cylinders and their components but also coolant passages and other necessary engine parts. The engine block was usually made of cast iron and was designed to be strong and to also provide a housing that prevented the leakage of products into or out of the combustion chambers. Because of the importance of avoiding leaks into and out of the combustion chambers, and because of the need for a strong casing, the engine block was manufactured as a single complex unit.
More recently, however, advancements in manufacturing have allowed for the use of a cylinder block with cylinders capped by a separate cylinder head. The cylinder head is mounted onto the cylinder block and often includes a portion of the combustion chamber for each cylinder. The cylinder head may also include openings to allow the combustion products into the combustion chambers. Because the cylinders in a vehicle engine are often arranged adjacent each other, the cylinder head usually consists of a single plate of metal that includes the various combustion chamber components and openings for multiple cylinders in the engine. The cylinder head is often made of aluminum strengthened by nickel.
The openings in the cylinder head that allow the combustion products into the combustion chambers and exhaust out of the chambers are regulated by intake and exhaust valves. Operation of the intake and exhaust valves is facilitated by an electro-mechanical system referred to as a valve train. A valve train generally includes the valves themselves and also various hydraulically-actuated devices for opening and closing the valves such as rocker arms, pushrods, lifters and camshafts. In a non-integrated valve train, for example, the hydraulic devices are electronically controlled. In many implementations, parts of the electronically-controlled hydraulic device are housed in a single “brick” structure. The brick structure includes many of the elements making up the electronically-controlled hydraulic device for the variable operation of the intake and exhaust valves, as well as all the ducts of the hydraulic system associated with that device. The brick often includes an aluminum housing that is secured onto the top of the cylinder head.
A cover may be used in order to enclose and protect the brick and cylinder head. The cover also prevents the leakage of oil from the brick and cylinder head to the exterior engine compartment. Historically, the cover's functions were primarily passive, with no active role being played by the cover. The cover may be made of aluminum or plastic.
The manufacturing requirements of producing and assembling a separate cylinder head, brick and cover result in a complex, expensive process that requires fitting and sealing together multiple parts. To avoid oil leakage, a tight seal is required between the multiple parts. Additionally, the cylinder head, brick and cover stack use a significant amount of the engine space available in a vehicle. Accordingly, there is a desire to reduce the complexities and size of the cylinder head, brick and cover stack.